PACIFICA — Police in San Mateo County arrested 12 people who agreed to buy booze for kids during an undercover operation.

The kids stood in front of convenience or liquor stores, made it clear they were under age, and then asked people to buy them alcohol. During the operation Friday in Brisbane, Broadmoor, Burlingame, Colma, Daly City, Pacifica, San Bruno, South San Francisco, and the San Mateo County Sheriff’s Office areas 12 people were cited, said Pacifica police Capt. Daniel Steidle.

The people caught in the operation face a charge of furnishing alcohol to a minor, which carries a maximum fine of $1,000 and 24 hours of community service. Police didn’t release any information about the suspects.

“Studies show the combination of alcohol and youth tend to increase criminal conduct,” Steidle wrote.

Otto Warmbier was arrested in January 2016 at the end of a brief tourist visit to North Korea. He had been medically evacuated and was being treated at the University of Cincinnati Medical Center when he died at age 22.